Apple doesn't typically announce a product update well before it's released; that would kill sales of the current model (per the Osborne effect). It's a different story if it's a brand new product category, like the Apple Watch or retina MB. This makes a hypothetical scenario of a March 15" MBP announcement with sales beginning in June very improbable.
Also, barring some huge delay in chip availability (which doesn't appear likely, as OSX7 pointed out), Apple is highly unlikely to release a totally redesigned 13" MBP before a redesigned 15" model. Early adopters are very price insensitive, so Apple will almost certainly make sure the first fully redesigned MBPs available are not the cheapest ones. Because of this, at the very least, it's doubtful the 15" model will be released LATER than the 13" one. For historical perspective, with the rMBP release, the 15" model came out 6/11/12, while the 13" wasn't released until 10/23/12.
