Readying an attack action deals with the spring attack.
It depends on how you implement readying actions. If the spring-attacking Wizard sees the Orc ready to stab him be might sit back and let loose with Magic Missile or some other ranged attack. Then poor Grog just eats that attack, anything from the melee opponents, and loses his action.
To get around that sort of meta-gaming pitfall you'd need to expand the readied action to include a fail-safe or conditional operation of some sort like, "The next time that Elf attacks I'm going to split him with my ax - or the nearest enemy in reach if I can't get to him." Or you could let the monster or character's the reaction be less precise, "I ready my attack for the next time the Elf takes an action."
If your caught in an area where your opponent shoots and runs you should probably run.
Tactically I think that option is going to be untenable in a lot of above-ground situations. Taken to the extreme any unit in light armor with ranged weapons should destroy any form of heavy infantry that tries to engage simply by falling back 30' and shooting, then watching the heavy infantry have to move-and-act just to get back into melee range, only to have them slip away again next round and continue the slaughter.
That tactical scenario should really only be applicable to horse archers vs. infantry - not infantry vs. infantry.
And, when I ran the playtest I described the kobold's attack as them swarming over the PCs - in my mind's eye I saw it like the effect in the cartoons when the tasmanian devil mauls someone.
I've got a real problem with 30-40 kobolds being able to all make melee against against the same two poor dudes blocking a 10' hallway. The Creature Size rules seem to imply an upper limit to "how many enemies can gang up on it" but the surround statistic seems largely irrelevant with automatic spring-attack. First rank hit, drop back 10', second rank hit seems perfectly viable - especially since I can't find any particular limit for friendly creatures sharing space.
Even fixing that won't stop the Dagger Barrage of Doom (TM), but at least you can charge up to the first rank of Kobolds and keep them from using the old "3 step drop" and throw on you.
In the end I think the rules are going to probably need to reintroduce the Charge action at the very least - probably Withdraw as well, with a penalty (grants advantage?) if you move out of melee threat without using Withdraw.
Leaving Melee: A creature that moves out of melee reach of an enemy grants Advantage to any enemy attacking him before his next turn.
Withdraw: Double your movement. You do not grant Advantage for leaving melee during your turn.
Charge: Double your movement. You may take a Melee Attack during this turn, after which you lose any remaining movement.
- Marty Lund