There isn't anything new that Apple would plausibly want to put in a MBP this year. The next revision to the MBP will be based on Broadwell CPUs and will probably support DisplayPort 1.3 (enabling external 5K displays) -- summer 2015.
No. Apple follows Intel's roadmap, any update there could be is about a year away.
Regardless, it doesn't matter when you buy a computer, really. Whether you buy it today or a year from now, give it a few months and something newer and better will come out. Unless you specifically need or benefit from whatever improvement the update brings, there is absolutely no point at all in waiting.
Open it! You have 14 days from the date of purchase to return it for a full refund or exchange, so you have nothing to lose if you open it now. If you wait till Thursday, and there is no new rMBP (which I highly doubt there will be) then you would have just wasted 3 days, where you could have been enjoying your new rMBP.