I think it's one of two things: either a) the designers just didn't think about "what comes next" after Kalarel goes down, or b) they did, and it got cut for space. Given the layout of the last encounter, I strongly suspect b.
Looking back on your posts, I'm starting to wonder if you're (erroneously) interchanging the following two concepts:
1. Changing basic game rules on the fly
2. Changing elements in a canned module on the fly.
If I change basic rules on the fly with no warning or discussion (oh, by the way, longsword only does d6 damage now) that's bad. If I do it only to give my monsters an advantage, that's best defined as cheating.
But if I change something in a module on the fly (let's say in KotS that if you defeat the Thing, the portal changes destination and can now get you to an alternate prime material instead of the Shadowfell; I as DM have decided it was the Thing's presence that was keeping the Shadowfell connection open) then from the players' perspective what's the difference? They don't, or most certainly shouldn't, know how it worked in the first place; and I just cannot understand why you think it should matter (or why or how it is "cheating") if I've decided at the last minute - improvising in response to their decision to try and go through - to tweak it into something more than the written module gives me.
Lan-"some things baffle me more than others"-efan
I agree there is something of a distinction between "you have 20 attempts to guess what I'm thinking" or "I have to answer honestly" versus "this is basis or definition for what I am thinking". The first are rules for the game, the second are guidelines to be followed by the answerer. Most all RPG rules are guidelines to be followed by the DM. However, that doesn't mean not following them isn't cheating on the DM's part. It just means they aren't explicitly "game rules" rules known between players to define their options when playing a game. Heck, in RPGs players really only have to roleplay their characters. There are little to no rules for them at all. Just like "try and answer the riddle" is the basic rule for most guessing games.
IMO most game modules must be predetermined in order to be roleplaying challenges for the players to face. Adhering to the damage output of a weapon is a guideline I cannot ignore without cheating in the exact same way I cannot change anything else that is predetermined, like the design of the map or the characterization of an NPC. Once the game has begun I don't get to change what was designed without essentially raising or lowering the pole vault bar before the jumper reaches it. It must remain the same throughout the attempt. Any aspect of an adventure may inform play throughout the challenge. Keeping it uniform for all the players means no part is subject to my whim once the game has begun. Can I set the bar beforehand? Yes, but not during the game.
The heart of the issue comes down to "winning" and "losing" which are meaningless in a game without a defined end. Even if the player's characters all get killed due to bad luck or poor decision making, if the players roll up new characters and continue the campaign continues.
Likewise when the dungeon is cleaned out and the characters return to town victoriously, the campaign doesn't have to end.
Winning and losing only have meaning if there is competition. As a DM I am not competing against the players. Some of the most fun I had as a player were sessions in which my character died. I don't look back on the good time that was had as a loss. YMMV.
The defined end is to gain XP. Or in a tournament adventure to accomplish the task particular to the adventure played like "kill the giants" or "raid the tomb", which of course gives points too. But these points aren't necessarily XP.
Points are given for acting appropriately even if what specifically earns a player points isn't known to them before or during play. In fact, I think that makes playing the game more challenging. If I only know the objective I am to accomplish, the the points I get for roleplaying other elements well becomes more e a matter of my skill as a player too. Not just the accomplishing an overall task or other acts I know which give XP.
If your PC dies, yes, I'd say you could continue in the game. But you certainly do not get to keep any of the points you earned from your previous attempt. That's true in campaign play as well as when playing a single adventure. I know tournament games do not necessarily let players continue who had characters die, but tournaments are almost always more rigorous than home games.
I suspect you may be characterizing a campaign as a story to be followed rather than a group of modules meshed into a "campaign world". If true, I don't think that's what roleplaying games are. IMO, storygames are for folks getting together to tell stories. RPGs are more about players getting together to be challenged through roleplay.
Don't you think this is kind of a mischaracterization?
Improvisation does not mean the PCs are guaranteed of success or failure. Yes, the DM could intentionally choose to throw too-easy or too-hard stuff at the PCs, but they could do that before the adventure was ever written, too.
-O
I don't believe it is a faulty characterization. I believe it applies for any guessing game designed. Just because we might take on game designer status and act like the judges on Jeopardy doesn't mean we get to rewrite clues and answers after the players start trying to answer them.
FUN FACT: If your players decide, on the spur of the moment, to teleport to a far-away city and go to the bazaar, you are cheating if you did not have the merchants' and beggars' names, products, motivations, skill at haggling, and cash on hand ahead of time. Because then it would not be a fair challenge.
-O
In campaigns this is (most likely) hopping from one module to the next. In one shots, anything outside the module is irrelevant. I think most home games put one shots in campaign settings to broaden the scope somewhat. But that still doesn't mean anything but the module being played is relevant to that module's design.
No, If your players decide, on the spur of the moment, to teleport to a far-away city and go to the bazaar, the appropriate response would be 'they can't, because it is not in the module'.
I disagree. Players can always elect to quit the module. But starting a new one does require a new module is prepped and ready to go.
Actually, this is why I believe 4E choose to go back to the old design of limited range teleport.