Due to significant system differences, it's quite hard to convert to 4E without either heavy reworking of one's own campaign material or without release of compatible campaign setting.
As it is now, WotC releases core books, while:
- WotC 4E setting is not available.
- delaying potential third party support materials.
Also, if one is not satisfied with WotC settings, one will have to wait quite a long time before being able to continue campaigning in their favorite world.
It's a wonderful business opportunity for Paizo and other OGL companies (they have been given more time to come up with quality alternative). It's a good opportunity to produce quick conversion PDF documents for those publishers who wish to switch from OGL to GSL.
Myself, I have already decided to postpone my first contact with 4E by 9 months (or even a year), in order to finish current campaign and to give everyone involved more time to release new stuff.
I am not excited with Pathfinder Alpha 3 (too many additional rules, balance changes) but they still need more time to come up with something.
I am not excited about FR.
I am unlikely to start gaming Eberron until I see official 4E version of it.
Necromancer Games products may be the only reason to be optimistic, but they haven't announced any 4E setting yet, so there is a reason to wait (my beloved Scarred Lands are, unfortunately, thing of past).
So, 9 months it is.
regards,
Ruemere
PS. I have Necromancer, Barbarian and Druid in my current party. Three more reasons to wait until PHB II.