They did confirm Season 6. Don't believe me? Check The Roundtable
Reminder that the Roundtable know just as much as you or me in terms of the show and all they do is promote news and make theories based on this news.
TBH, I personally see this as rather a speculation, beside even if this is speculated as the real source, i wouldn't take anything from that said youtube user says. But all i know that they needed to get over with this nerve-wracking hiatuses so that the fandom would just shut up for all of the complaints in the world, heck look at Star VS. Fandom, they're not the only ones that are waiting for the hiatus to end, which they had held 4 months since July, at least DXD gives reruns, unlike CN, would wastes time with reruning both Teen Titans (OG and the GO!).
Any of the Gems could get this song - but it seems like it's most likely Lapis, given the lyrics "awful place" and "rather be free" sound exactly like what she'd say. Plus there's the whole trailer from SDCC, which shows Lapis prepared to fly away.