PS: I talked with Mike Hearn about this idea, he mentioned that the main problem with Extended Addresses is the scanning part. For SPV clients scanning new address is not that easy. My proposal for that is that wallet software use a insight-like API service, from which balances of arbitrary addresses can be pulled. If the use dont want to use a public API service, they an run their own Bitcoin full node (services like bithost.io allow to run a full bitcoin node, at very low cost) and add insight-api or other blockchain API service on top of that. Probably services for bitcoind+insight will appear soon also.

PS2: Thanks to @maraoz to reviewing this post and for his valuable comments.