The March date is way off for a new design. Maybe a minor update around then but I anticipate the redesign to announced at NAB in April. That's late enough for Montevina then (just).
Howdya know they haven't been working on a new design for years? Having said that it would be strange to release a NEW MBP (rather than 'new' - merely boosted specs) so soon after the MBA - unless they were released together.
All this stuff about stuff being released only on Tuesdays - how much truth is there in that? I'm sure i've head 'rubbish - thats not a tuesday' way too many times, often to no avail.