I think Lyles will be on the team, but the Spurs are also in a position where they could need clearance under the tax. There are three main ways to get that clearance, and waiving Trey is the most palatable (other ways being RJing DeRozan and letting Poeltl walk). If the Spurs draft any PF, the position becomes crowded with Gay, Sam and Lyles all on the team, and that ignores DMDR and even KJ getting minutes there. I think the team feels confident that Lyles gives them an okay floor, but I doubt they see him as a long-term piece.
I don't necessarily agree. There are a couple of guys like Neismith who might immediately compete for minutes, but I agree with some other posters here who think Sam is ahead of most draft picks. I want the Spurs to draft someone and make rotational minutes for them. But I also recognize that there are some guys who might not necessarily have a place on the current squad without some restructuring of the roster. Guys like Precious, Poke and Williams for example aren't nearly as equipped to be bit role-players like Sam could be if he gets that shot down this summer. There's more upside to putting them in the d-league than there would be for Luka.
I know you're way more inclined to cleave to positional absolutes than I am, but I don't disagree that he seems more like a four than anything else. I do think, however, that Pop put very little stock into those designations. People talk about him always playing small, but it was just last year (2018-2019) that he tried to start the season with DJM/DMDR/Gay/Aldridge/Gasol as a unit. I don't think he'd shy away from Samanic/Gay as forwards at all. I don't think it'd be a great long-term thing, but it definitely feels like a worthwhile gamble and a way to add length to a second unit that has to compensate for Mills and Gay. Mills/Murray/Sam/Gay/Poeltl is an interesting unit if Sam can shoot well enough to space the floor. Foot speed would be the most obvious issue, but the size might really help. It's not an everyday unit, but it would work against some teams
And if Poeltl walks, then I think you'd see a whole lot of Mills/Murray/Walker-Johnson/Sam/Gay lineups rather than running with Eubanks or the min center the team replaces Jakob with. Or if Lyles slides down and over, the starting PF job is back to being open again.