This is how I see it, OW2 most likely started gaining focus from the team after the second or third anniversary.
Overwatch’s initial popularity started fade out after 1.5 years since it’s release.
The meta game itself was stable according to their data until the 3-3 meta. Their data was stable, but the community was outraged at the emergence of 3-3. So, they thought about potential solutions and role lock was the path they chose.
Because of how role lock is meant to be a long lasting investment this was actually the best choice they had if they were primarily working on OW2 at the time. If they worked on OW2 and OW1 on the same time with varying focus, there would have been, probably, more buggy patches and unbalanced changes.
Focusing on OW2 is, in my opinion, the best choice here because after they finish it and it releases, OW1 will get the same engine as OW2, which means they can really focus on making sure the game is balance and they can pump out more balance changes, new event content, and get more ideas for cosmetics for the events as well. This is the best case scenario to me.
THE NEXT PART IS A COMPLETELY OPTIONAL READ
On another subject, since it's kind of relevant, is OW in general becoming free to play. I see many different negatives to this idea. But I do see the successful potential of bringing in more players and revenue. However, I think the negatives heavily outweigh the positives. First off, the micro transactions, They would have to find something other than loot boxes. For instance, WoW's subscription fees, unlikely but possible, pay to unlock heroes which is extremely unlikely, and the most possible one, make exclusively pay-walled skins like OWL and they would HAVE to be limited or event exclusive to get people to buy them. Next is the influx of people smurfing of making alt account more often because it's impossible to figure out if it's another person's email or the same person, but just on a different email. The last one I can think of is the company really. If they do this and it's successful, they're going to do it again and it's possible for core members of the team to leave because of this. The quality of the game has a chance to fall in quality and I don't think any of us want that.