They didn’t think this last year; why would they think so now? There’s really no one new to push him down/off the depth chart.
It's not about another WR pushing him off (although I think Fehoko is above him on the depth chart). It's more there are other players they will want to keep on the 53 that they think have some value or a better chance of being claimed on waivers due to positional value.
For example, they may keep Mustipher (who has had a good preseason) on the initial 53 over Weaver because rotational DT's have more value on waivers than a WR6 that isn't a special teams ace. Weaver would almost certainly make it to the PS, the main risk would be Weaver choosing to sign to another PS. In which case, big deal.
But as I explained above, with the call up from the PS they can keep him there and call him up on a weekly basis if they have injuries or feel he can contribute.
As the DL get healthy they can move Mustipher to the PS in a few weeks when rosters are more settled and he's less likely to be claimed.
This is just an example, what I'm trying to say is that it's no longer a case of "This is our best and most balanced 53". With the way the PS has changed it's added complexity to how teams choose their roster.
An extension on how we cut Aaron Brewer a year or two ago with the intention of bringing him back because nobody claims a long snapper.