Its always possible for something to change. But, I think it's almost certain (96% chance) that 1.4.5 will come out on all platforms at the same time just as 1.4.4 was.
This is due to how all of the platforms are caught up to each other in terms of game content. In the past, a large gap between PC and Console/Mobile developed due to past generation device limitations as well as changing the Console/Mobile developers. For awhile Console & Mobile were on "catch up", but that gap was sealed with 1.4.3 and it also allowed DR Studios to get 1.4.4 ready for consoles even while it was still being developed on PC, so I think it is very likely such a gap won't exist anymore for Terraria.
If 1.4.5 also includes crossplay, then all the versions will have to be the same as well. Crossplay itself still remains as a "maybe". Hopefully it will come with 1.4.5, but it is not guarenteed.