It's possible, though we've had some content (e.g. Runes Reforged) on PBE for extended periods in the past without major fatigue issues once stuff's live. Most players don't engage much with PBE content, so the hope is this leaves gameplay changes feeling a lot fresher at season start for most players
Tournament of Souls - we feel this one went quite well overall, and really happy with things like this as alternatives to the visual novel format that was feeling played out previously. Technical issues are the exception though, while it worked well for most players it struggled or simply didn't function for others, which is definitely something we'd want to do a lot better at for whatever's next in this vein