With current roster they have I don't think they need Giannis on their team.
I guess what they need is good rotation since they already have good shot to win a championship this season. If it happen that they trade their young valuable piece its like they are risking their future. Knowing KD he usually leave especially if he think that he's on losing team. So best to retain everyone and focus on their development. Let KD lead them and they might get good experience from a veteran star like him.
Agree to that, knowing KD better not to take that risk as he can easily decide to leave if he thinks that there's no chance of winning, just look on how he abanoned both Nets and Suns, after these two squads brings him to have that chance but did not materialize, now, we again see another transfer and this time to a much younger team who shows decent performance last season, a matter on how the management especially the mentor who will guide them together.
So its better for Rockets to retain their current roster and not to push any trade just to get Giannis since it will just ruin their organization then they might undergo on rebuilding process for long time again.
They already have the best assets that could able to deliver them a championship and what they need to do is to work out on their team chemistry so that they would became more effective on each play they set.
KD is I think enough since having two big stars on their team might create chemistry problem.
They even hadn't play yet, so they have to see if KD is a perfect fit for them before they can think of like having to get Giannis first. So it's very interesting to see how KD will be with the Rockets. Houston already sacrifices here, trading Jalen Green, the supposedly franchise player. So they have broke their core already and then now moving to KD era. Maybe after this season, if the gamble has paid of or not for the Rockets and then maybe that is the time that they will have to shift pieces and who knows, possible for them to get Giannis + KD. But for now, let's enjoy KD with the Rockets and see if he can bring them to the West finals.