The ��hp is a future classic and will only go up in value.
IMO it deserves to be. It was probably the most fun car you could have bought brand new in 2010 for under £8000.
Many 100HP's will by now have had various modifications; some well considered and thought out, others less so. To be of any interest to a true collector, the car will need to be kept original, so you can forget about upgrading the suspension, fitting different wheels, or remapping the engine if you want yours to become a proper classic.
I think prices have probably bottomed out now for well kept cars in original condition and if kept that way, you'll likely see a modest increase in its long term value, but don't expect it to be worth a fortune anytime soon.
Have a look
here at what the pundits think about the original Panda 4x4 as a potential classic. There are some similarities here; when new, the 4x4 Panda was far and away the cheapest 4x4 you could buy, in the same way that the 100HP was easily the cheapest non-pedestrian hatch in any car dealer's showroom.
In the final analysis, the 100HP is basically a van version of the 1.4 500 with rear windows and back seats. If you want the drive of a 100HP, you can get essentially the same experience by buying a 1.4 500, and I don't see 1.4 500 prices rising anytime soon, as that car will always sit in the shadow of the A500.
I think anyone buying a 100HP now and looking after it will always get at least their original investment back, but I wouldn't want to rely on it being part of my future pension plan. I'd say these cars are best enjoyed in the present for what they are.
Owning a classic with any real value is actually quite limiting; unless money really is no object, you can't enjoy it to the full without thinking about how much you'll lose if you actually use it.
A Capri 280 with under 1000 miles on the clock sold for a record £54000 in 2016, but what are you going to do with it that isn't going to destroy what makes it valuable? You can polish the fenders & maybe take it on a trailer to classic car shows, but that's about it. It's going to spend the rest of its life sitting on blocks in a dehumidified garage.