I checked the specs of the T420 and it looks nice, but I'm concerned about screen quality and lack of newer features like USB 3.0. It does have an esata port but the rest seems like a feature list from a mainstream dell. It does have the legendary thinkpad construction but otherwise the feature list is rather mundane. The same sort of gripes I have with the new MBP apply to the T420... Nice package, lacking in up to date tech and interfaces.
I want to see the replacement for the T410s. If they can get one of the new i7 cpus in there, I'd probably be able to accept the other missing features. Unless toshiba's R700 replacement has USB 3 and all the other latest and greatest interfaces along with the i7. Then I'd have to think really hard about which one to get. The T410s was harshly reviewed for short battery life, while my wife's R700 gets 5 hrs easily and had an i7 option, in roughly the same size package.
The 13" MBP is still very attractive, but I think the new interface standard is going to have to mature very rapidly to make up for the lack of USB 3.0, esata, etc. And that means intel will have to let other manufacturers use the standard sooner rather than later, which means more choices. The fact that the T420 lacks both USB 3.0 and the new interface is not a good sign. I've seen ads for the new interface popping up all over the internet in the last week though, so maybe other laptop manufacturers will be allowed to use it fairly soon.