There are a few rumors floating around....
1) That the MBP will get the Mag latch, etc, minor design revisions from the MacBook. There isn't any particular support for this in terms of when it will happen. but it seems fairly likely that it will eventually happen.
2) More compellingly, there have been persistent rumors surrounding a smaller notebook of some kind than what is currently available. The rumors vary widely from a tablet to a subnotebook to a 12"-er, from a relatively conventional design to one that uses a Flash hard drive, etc. Generally the part most people agree on is that it will be a follow-up to the release of lower power consumption versions of the Core 2 Duo -- either a couple of variants that Intel is releasing this quarter or the "Penryn" variant which is a bigger leap in this regard, but is not due until later this year.
I'd put much less credence in anything beyond that. It's unlikely for instance that the MB will get an external redesign. Deal with it.