If you have some storage space that you would otherwise have anyway and if it takes a negligible part of it, I'd store it away. It needs to be dry storage, with no damp air rising from floor, as people found out, typically when storing a car for years in a barn damages it fundamentally. Selling as you found won't bring in $s to make a significant dent when buying new bike, also what you get for the bike now, you very simply won't 'have it' some years down the road (to use it towards purchase then). Your financial situation is likely not such that having the sale money or not will make any real difference.

If you store it and in the future will find you want something else to ride, chance is the resale value then will be much higher than it is now, due to it being even more vintage. I'd sell only if you think storing would be in some way onerous in longer run.