Note: There is no official information about 5th Edition, here. This is merely some thoughts on the direction I would like to see WotC take. I guess think of it like me throwing ideas around to see if any stick (or if anyone else has a better idea).
Powers are a really nice 4th Edition addition, especially for classes previously that did not get many options, were rapidly eclipsed by spellcasters, and/or lacked the "scalability" to remain viable for more than a handful of levels (coughfightercough). It was nice being able to make a fighter, rogue, or ranger and have interesting things to do that helped separate you thematically and mechanically from each other instead of spamming a routine melee attack over and over. My problem with the power system was that for all the powers that exist, there are still occasions where I cannot create the character I want without having to invent my own powers. This is fine for me and mine, but I know that groups that only allow "official" content (and not even all of it) are legion.
What would really fix this whole power bloat issue, while helping ensure that players still get what they want, would be for WotC to just give us a formula or system that would help us create our own content. Like, recommended damage, conditions, ranges, effects, etc. It could be a point system, where you just buy everything with a power budget based on the level and power frequency. Keywords could be used to restrict effects based on power source, so that martial cannot get their grubby hands on teleportation. Also, a shitload of examples with components would be handy (and allow for drag-and-dropping other elements) would be handy.
They could also try moving away from the power system as-is. I would not mind seeing something along the vein of Essentials, where martial characters can choose effects or kickers that they could add to their attacks like power strike. They could adopt a power-point like system, so that martial characters utilize "stamina" or something to boost their attacks. This would make things more flexible and help avoid the whole "argument" of why you can't hit something really hard more than once (not that I paid any heed to the latter). While I wouldn't use it for every class, I could also see this being applied to wizards using a magic point system, and there could possibly be a mechanic for burning healing surges to give you a stamina/magic boost (kind of like 3rd Edition's Body Fuel feat).
Someone also suggested using pre-reqs for various powers, which sounds similar to how Exalted works. Some powers might require a combination of ability scores, so fighters would need a good Strength and Dexterity for heavy blade powers, or good Strength and Constitution for hammer and axe powers. Hell, you could just make a huge-ass list of martial exploits and let rogues snatch up exploits thematic for them, while allowing characters with good Intelligence or Charisma nab leader-like exploits. Want to take it a step further? Skill training could open up more stuff, or if you want skill ranks (whether numbers or descriptors).
What do you think?