I personally think that give it another few years and it will definitely be something more of a 'collectors item'.
At the moment here in the UK, I am seeing a lot of them being broken for parts - maybe when there is nothing really wrong with them. Seen a few going for breaking because of silly things like head gasket gone.
Heard of a 2001 that's going to be scrapped and there's NOTHING wrong with it... It is going to be scrapped because the people who had it didn't pay a garage for work, so the garage is selling it to someone I know at the cost of parts that they put in to fix it over a year ago. They've told him they want it scrapped, to 'teach the owners a lesson' even though after not wanting to pay for a couple of EAS items, apparently they went out and bought a brand new RRS...
There is a lot of people in the UK that I deal with that have the attitude of 'they're not worth fixing, and worth a lot more in parts' which sometimes is true.. but every one that gets broken for parts means there's one less P38 on the road, which as they become rarer, I believe the value will go up.
I have also heard (but not confirmed) that there is a company around Oxfordshire somewhere that completely refurbished them. Replaces any work/broken parts with genuine brand new etc. Was told that cost of restoration is around £80K!!!! The guy I was talking to asked them what the market was for a P38 like that... The answer was 'wealthy people who have had newer ones, and haven't liked the styling/reliability/finish etc of them and wanted a reliable P38...
So I definitely think there is a market out there for GOOD P38's - and in the next few years, as the major issues with the newer ones start to present themselves, and parts prices are horifically expensive, and less easy to 'DIY on the driveway' like a P38, then I believe this will also push the cost of a decent P38 up.
I know I'll be keeping mine for years to come, as I'm in no position to purchase/maintain a newer model at the moment, and I love driving the P38. It has character, unlike the newer vehicles. (had a lovely new Audi A6 as a rental vehicle back in August and whilst it was immaculate and modern - just had absolutely none of the character the P38 has. I couldn't sniff at the 56mpg fuel economy though!)
I guess time will tell though but that's my 0.02
