3.5 is due out this year, so if there is anything planned or even in the works on 4.0, you're not going to hear about it.
3.5 has a beta out. It's not feature complete, but we know about most, if not all, of what will be in it. There's some designer enhancements and fixes, but I'm not at all sure that even then the VS designer will be as usable as we want. Just my opinion, and I'm not affiliated with Microsoft, or even an insider, so take that statement for what it's worth.
Also included in 3.5 will be a lot of the "missing" controls. Given those, I'd say WPF in some ways will surpass WinForms (I'd almost make that claim today, actually), but others will disagree due to the designer. If a designer is important to you, I'd recommend you use Blend, which actually surpasses the WinForms designer, though developers may find it a foreign tool to use.