at the moment there probably isn't a team leader per se. i mean, fury is still around and the movies never really established one specific team leader. stark was probably the defacto leader simply because he was basically the first member (even though fury said he wasn't cut out for playing nicely with others way back when) but he definitely defers to cap in battlefield tactics.
but honestly, rhodey, black panther, thor, dr strange could ALL take the leadership role pretty easily, but they also all have other obligations. hawkeye could? the movies haven't really shown that quality in him but the comics sure did. but he's always been more of a lone wolf so probably not. they probably WON'T have a team leader. more of a knights of the round table type of thing where they consider themselves all equal with different strengths.
gamora WAS there at the end, but it's pre-GOTG gamora. she obviously knows nebula, but she has no idea who any of the other people are. so it's a fair assumption that she'll be around and fight the good fight, but she's not the one that peter fell in love with. not yet at least.