As it had been discussed here before, there are methods to compress the entire blockchain state on your disk (ATM to like 500MB), yet still allowing your node to have a secure copy of the entire UTXO db and thus all the possible address balances, as well as be usable for mining. Which SPV clients are totally useless for - they are just leeches of the bitcoin network and they should be banned, not encouraged, IMHO.
But to do this, you need to extend the blockchain protocol and to extend the blockchain protocol you need to change the reference software, and to change the reference software you need to talk to the people who have their own agenda - which have recently seemed to be quite contradictory to encouraging decentralization of nodes.
All it takes is just make a hash from serialized records of the current UTXO database and mine into the next block (each block, or once for awhile) - then enforce the protocol to verify this hash and reject blocks that would have a wrong hash. It isn't a rocket science - quite a simple feature actually, comparing to the rest of the bitcoin protocol.
Last time I moved this topic on this forum, I was told that they "way ahead" of me with the solution.
Though that was like over a year ago - now they obviously must be at least one year further ahead of me...
![Wink](https://bitcointalk.org/Smileys/default/wink.gif)
Anyway, don't expect it to happen within the next 10 years - not with this team, and ATM there isn't any other bitcoin software that would be suitable for mining.
And there isn't any solution for the disk space problem that could work securely without first upgrading the blockchain protocol (inside the mining software).
So if you want to keep running a bitcoin node like 5 years from now, better start monitoring hard disk prices already.
Then use the same rule as for bitcoins: buy when it's low.