We would really need to know what sort of head unit you are going to buy to answer that one! are we talking after market or VAG?
If we are talking VW units then they will still work but if you go third gen RNS510 RCD510 etc then you need to chnage a wire position in the little blue plug to get the right sound quality.
If you are talking after market I dont know but Im sure there are converter boxes out there for certain stereo brands that would allow compatibility.