1.5.5 is currently in a "staged" rollout, right now at 20% of all devices.
For "sync all" -- well, I could add "wider" sync window settings for old events. Note that events in the future are always synced, and so do recurring events, no matter how old. I think this should cover people's needs.
Regarding "turn sync off, events not deleted" -- not sure I see the usefulness here. Once initial calendar sync is complete, each subsequent calendar sync is incremental, takes very little time and traffic.