What are the odds of that? At best, 50/50, I think. By my recollection:
Core Duo: Compatible.
Core 2 Duo: Same socket, but not compatible with early Core Duo chipsets.
Nehalem: New socket.
Westmere: Compatible.
Sandy Bridge: New socket.
Ivy Bridge: Compatible.
Haswell: New socket.
Haswell refresh: Compatible.
Broadwell: Same socket, but not compatible with early Haswell chipsets.
So basically, they're changing the socket with every non-minor-speed-bump release, and with some of the minor speed-bump releases. This translates to about a two-year incompatibility cycle. Most people don't upgrade their CPUs more often than that, so in practice, motherboards are now disposable even if you build a machine yourself. The only things you can usefully reuse are the case, the power supply, and mass storage devices.
IMO, the entire industry might as well switch to soldered-on CPUs. There's no real advantage to socketed CPUs at this point, given the relatively short upgrade window. Ditching sockets would halve the number of SKUs (no need to stock the CPU and motherboard separately), would reduce effort for system builders (both in choosing parts and in installation), and would improve reliability.
There's a downside, of course. Most Haswell machines on the market draw 30W idle consumption or higher. At $0.38 per kWh (what I pay for additional consumption), assuming the machine runs 24 x 7, that translates to $67 per year more in your power bill, or a couple hundred bucks over a three-year product lifetime. Heck, the Alienware I looked at idles at 46W, or $120 per year more in power costs. That adds up rather quickly.
I'd *love* to find a PC that draws 10W or less when idle, with a desktop-class Haswell Core i7. In theory, I'm told that it is possible to build systems that are roughly in that ballpark, but most of the systems out there don't get close.