The 13" MBP has a low res screen - I would either get a 13" MBA or a 15" MBP+.
I think the 13" non Air models are 'end of life' and will be replaced with some sort of Air variant next year.
Adding an SSD to existing machione would be a good cheap stop gap though.
I'd disagree.
A lot of people choose between the top spec 13 inch and the bottom spec 15 inch MBP, so it's certainly a big seller.
The 13 inch MBP is the most portable and has critical things such as FW800 and the DVD Drive, which the MBA is totally missing. It's not going anywhere unless they put such things in a MBA, which they won't.