Hey there! There are currently no news about this. I would recommend to wait until Beyond Light launches. In the mean time, I would recommend to grind out your power level so you are prepared for the upcoming missions.
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At this time, Bungie hasn't announced anything with regards to character boosts, or the power level floor being raised as happened with Shadowkeep/New Light. A note on character boosts: Typically boosts are only available when one of your characters reaches a certain power level. The boost would then be used to bring your other characters up to boosted power level.
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No, your main character would need to reach either the soft power level cap, or the power level cap. Currently, these are 1000 and 1050. Next season it appears to be 1200 and 1250. Once that was achieved, a boost would bring your other character(s) up to the boost power level. I'm not sure if boosts are still available, however.
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I wouldn't expect a response on these details from Bungie outside of the This Week at Bungie news posts. These are released every Thursday in the afternoon Pacific time, which means there will be this week's and next week's prior to Beyond Light's launch. However, if I hear anything from a citable source, I will let you know.