It has be confirmed that there will be connectivity to the fourth generation because there is going to an in-game event that is activated by a special event legendary dog. This will also allow you to connect to the third generation with the fifth and because the fourth generation will act as an intermediary. On the topic of a pal-park in the fifth generation I think it is 50-50 chance that a pal-park is included because of the lack of GBA slot on the newer Nintendo DS versions.I honestly think that there won't even be trading with 4th-gen. The only reason Pal Park worked was because you couldn't trade them back to the GBA to take advantage of the physical-special split, move tutors, etc.
With new move tutors, new movesets, and likely new abilities for existing mons, I think trading with 4th-gen would be too much to implement without breaking 4th-gen. This would also mean no Pal Park.
Besides, 4th-gen has no data for Isshu. I haven't tried importing any from Colo or XD and then Pal Parking, but I heard there's no Orre data either.
Well, I think that they should include it for people like me who still have DS Lites because A. They can't afford it. And B. Because they don't really care about getting the newest versions of stuff.
the black and white versions should come with a DSi channel download. (kinda like the Mario kart channel on the wii) this channel will allow you to deposit Pokemon from other games like D/P/P and SS/HG onto it. then when you plug B/W back in you should be able to access it via a pal park!