So, the Suicune capture can go two ways:
Gou legit catches Suicune and it will start living at the Sakuragi park.
Gou catches Suicune but he releases it quite soon afterwards due to realising it’s got the duty to protect the lake or something along those reasons.
After JN052, I can see Gou doing the latter one. He did, after all, give away his Dugtrio to Endo due to noticing how big of a importance the Dugtrio had as a leader to all those Diglett. Also after noticing it’s a perfect partner for Endo :) Good kid, this Gou.
We’ll find out this friday. ONe thing is for sure: he is catching Suicune for real, pokedex entry and all. All that remains to be seen is whether it’s temporary.