A billion years is ambitious, but I think the whole point of it is that by setting so far in the future he has created a setting where anything goes. With that much time for civilizations to rise and fall and technologies to be developed and lost and species to evolve and go extinct, you can do anything you want.
The only thing you can't do is set an adventure in post apocalyptic Manhattan or the ruined Vegas strip. It stretches my suspension of disbelief too much to imagine that anything constructed today will last a billion years. This raises the question of why bother saying it is Earth? Call it something else and make that a Big Campaign Secret that the GM can let the players discover at some point.
If he had left out that it was Earth after a billion years, I don't think there would be any criticism of a science fantasy setting that had existed for a billion years. It's only when we had that tiny bit of reality to it that our suspension of disbelief is challenged.
I do enjoy the discussion of what Earth will be like a billion years from now, but I don't think that's really the point. It's really just "some time far enough in the future that all kinds of crazy stuff has happened."
I think it sounds interesting. Reminds me of Thundarr the Barbarian. I'll wait to see more details before I decide if I want to support.
Mostly I'm stuck on the list of bad ideas in the Game Play page.
1. Modifying DCs is not in any way easier than adding modifiers to a die roll, except that now one side of the exchange (the GM) does 100% of the math. Math is math, guys. A big pile of player-triggered modifiers are still going to slow down play, whether that math is done on the "front" (PC) end or the "back" (GM) end.
2. Spending experience points for short-term benefit is something I straight-out hate. The only variation of this I've ever been okay with is in Over the Edge, where they're "temporarily expended" (for the duration of that session) but never permanently lost until you spend them on actual advancement.
3. Color me very dubious of spending XP to increase character abilities OR advance in level. What's going on here?
4. The last paragraph is what you might call "unintentionally too honest." The paragraph before it talks about how easy everything is, only to follow up with "you know I never like to make things easy." And yes, I do think that Monte's past work is a great example of never making things easy - good lord, but Arcana Evolved (especially with its splatbook) is a clunky monstrosity of bookkeeping at mid-to-high levels, even more so than core 3.5. Playing Arcana Unearthed/Evolved for the past, um, seven years or so has revealed a LOT of rough edges and oversights.
I will certainly be curious to see where this goes, but oy.
Looks cool... as an astrophysicist I cringe when I hear "a billion" years. I don't know if he understands how long or not long that is considering what he's said about it. 8 great ages have past on earth... Now it took around 5 billion years for life to advance on earth as it has. Humans go to where we are in what... ~12,000 years? Around 65 million years is when the dinosaurs had their heyday. Now im no anthropologist but A billion years is... I ... ugh.. I Dont even know it just seems like he picked a large number and said Eh...... there's also several other things to think about, considering the moon is going to be much farther away from us then ( if it isnt gone altogether from some rogue comet or something), Saturn wont have rings, the sun wont quite be red giant yet, but it will be past mid age... I can't imagine the earth being anything other than a desolate wasteland ( of course you can say SCIENCE-MAGIC and take care of that) . I dont know, im definitely curious just to see how much thought was put into it.