Just sell it on eBay after 3 years and get the next thing.
I think resale of these machines will not be that high in 3 years. There's a lot of people out there that will buy an older machine, for whatever reason, and upgrade it and be fine with it. I for one just bought my wife an old white MacBook off Craigslist ($300), spent an extra $100 on 4GB RAM and an aftermarket battery. Now she has a machine that is more than capable of handling her needs and I'm not going to be hacked if she spills coffee all over it or loses it. In a couple of years when she's ready for a new one, I'll put a new battery in hers and give it to the kids. Wouldn't be able to do that with the new MBPR.
Also, remember a lot of times Apple specs say one thing about the max capacity of the RAM and then a year after the machine is released, memory manufactures come out with new sticks that surpasses Apple specs. Again, I just dropped 16GB in my MBP (early 2011) for <$100, even though Apple says it'll only handle 8GB, never mind Apple's outrageous prices on upgrades.
It wouldn't surprise me if they eventually make some of this user serviceable in future models. My 2007 MBP was not supposed to be user serviceable other than the RAM. On the current MBP the owners manual tells you how to swap out RAM and the HD, so they changed there.