on a serious side though the BMW E30 was a massed produced square box and production ran for around 9 or 10 years and they have received a classic status so I would like to think that there's less Audi A4 quattros in all guises than there was E30's so you never know.
with a quick look theres still at least 5000 E30 325i's ( thats counting basic i's se's and sport's ) on the road fair be it there will be a lot of them bodged up drift chariots but they had a longer production run than the B5 A4
the quattro wasn't a massed sold one so there was less B5 A4 quattros brought into the uk than there was just 325I E30 bmw's possibly on the road at present..
I would say the quattro A4 has a good chance at classic status
I will be amazed if they are ever worth more than £4000. Lots will be scrapped as the front arms will put people off repairing them.
If you are holding out to make some money you have the wrong car.
How many of your friends want your Audi or think it is special. Very few of mine have any interest in it, even then look at how active this forum is. Compare that to say a Lupo GTI. They sold about 900 and people hanker after one of those and the prices are very strong too. Their forums are far more active than the A4 one. Most think I am mad holding onto the car for as long but to think its in decent condition and have been surprised at its reliability.
I will probably keep mine forever as its worth more to me than other people and I like tinkering with it. I will always have other cars to try though.