Because my HDD cable is bad, and when it died it corrupted my internal HDD. I was able to recover the data, but it is not spread across two machine. My 2012 is falling apart - 4 holes in bottom where feet came out, holes in the keys, bad keys, dim monitor, etc.
You sound like you needed a new computer a year ago... (What have you been
doing to the poor thing?)
Personally - yes, since you've waited this long, I'd wait until after Tuesday
just in case but its 90% certain that it will just be iPhone and Watch so don't hold your breath.
Bear in mind that:
Even the "old" 2015 model will blow your 2012 model out of the water with its display quality and speed - the CPU and graphics will be measurably better, but the night-and-day difference in general use comes from the SSD. Normally, I'd say you could squeeze another year out of your 2012 by putting a SSD in it, but since it sounds like its being held together by duct tape and good intentions, maybe not. The 2015 model will be a decent upgrade for you.
The new model, when it arrives, is
not going to be twice as fast, half the size, have 5x the storage or otherwise make the 2015 model look like an antique typewriter. The "skylake" CPUs are only a modest improvement on the old ones. It should be a
bit better all round but its not going to be dramatic. There might also be some compromises - Apple may decide to "improve" the keyboard by adopting the ultra-thin MacBook design or make other changes which are a matter of taste.
Its likely (but not certain) that the most significant change on the new model will be the replacement of some or all or of the existing ports with combined Thunderbolt 3/USB-C ports. This is good "long-term" as USB-C is likely to be the emerging standard for connecting everything from disc drives to displays, but in the short term be prepared to spend a small fortune on adapters for your existing equipment (esp. Thunderbolt 1/2 stuff which will need a $100 adapter).
So, while the current model is a bit overdue for an update, its not the lemon that some people would have you believe - and if its destined for the same treatment that your 2012 got I wouldn't worry about whether it will still be viable in 5-6 years' time, since it will probably be scrap by then.
Why not get a refurb 2015 model and save a few bucks so it won't feel like it has "depreciated" so much when the new model comes out?