Not a chance. Absolutely not. Why should ArenaNet remove one of the key reasons to get out and explore the world?
I love exploring on alts. Reminds me of areas that I have not been to for ages. Additionally, selling gifts in the Black Lion Marketplace would simply add another element of P2W in this game. Legendaries are top-tier weaponry (yes, I know they're the same statistically as Ascended weaponry), therefore their gifts should not be available for money.
Yes, I am well aware of the first generation weaponry being available for gems if you convert them to gold. I have hated this for years but there is nothing I can do about it. However, if my comment helps to prevent the gifts becoming available for gems, I'll take that as a small consolation prize.
TL;DR: No, you can't have them in the shop. Play the game. Stop looking for shortcuts.