I think that for 4e to be worth it there should be changes on the same scale as 2e ->3e. The kind of tweaks that many people on this thread have suggested seem like a ridiculous idea to me; no more than a 3.75e.
Like MEM I've been very impressed by design changes that have been made in SWSE - in class design, in skill design, in changes to melee combat.
I'd love to see similar new thinking applied to spells and magic items too.
If I was doing some imaginary 'blue sky' thinking, I'd like to see:
* Better mechanical support for adventures other than killing things and taking their stuff
* Better support for epic play (i.e. not just bigger numbers, but bigger adventures)
* elimination of buffing magic items, instead see fewer items which scale with their user better.
Not what everyone will want, of course!
Cheers