A lot of People think that it's nice to keep the bike as it is, as long as it's serviceable and not decaying in front of your eyes. I have a Raleigh Royal that has quite a few battle scars but I only use it for foreign tours as I don't trust baggage handlers. This year they managed to put a dint in the crossbar.
However I like my bikes to look as nice as possible and if I could afford it and had a bike that I was very keen on [a keeper], I'd have it resprayed.
Selling it on is a gamble. I would not spend the money with that in mind. I've seen some very nice resprayed stuff go on e-bay for not much more than the respray and build cost, or less!