Keep him, it’s a great condition Tri Logo that is quite difficult to get hold of, as Scruffy has alreay said.
You will kick yourself if you sell it (unless it was to me of course)
Nooooo, he'll kick himself if he doesn't sell to me
As for rising values, that's always a tough one. SW collecting, like any collecting, experiences cycles. Something will become flavour of the month, prices will double or triple then everyone has one that wants one and prices drop off a little. We've seen it with VCJs that were hitting as high at £2k loose and are now back to more like £1,200. OK, not the £600 they were 18 months but better than £2k.
Trilogos are enjoying a longer run of popularity and no reason to believe prices will calm down anytime soon. I wouldn't advocate holding onto it for purely the purposes of profit but I guess why not? A far better idea would be to start collecting them. You've already knocked a bit of a tough one off the list so carry on. You can buy TLs for as little at £30-£40
What sort of trades are you after for him? If it's loose you want I have quite a lot of spares....