It can't cause a dump because it's coming in with empty hands. You need to have coins first to be able to dump them into the market.
Bakkt won't dump, but the 'buy the rumor sell the news investors' will, which doesn't really seem to be the case right now because it's already calculated in the price already. In other words, news is sold already.
What we experience right now is normal price activity, which is just as bearish as it has been for the last couple of weeks. If we dip below $9.6k, I expect another touch $9.3-$9.4k touch which is the horizontal support level of the current formation.
I expect a full break any time soon that will bounce up from $8.5 to possibly $9k to continue making lower lows after some sideways consolidation. Bitcoin's chart looks like it wants to make lower lows badly.
I was also one the many who hopes that Bakkt will bring the btc price to the new level and I was waiting for a year for this to happen but now I'm just really disappointed. Maybe you are right that the rumoured was already bought at the same time where bitcoin has rose $3k to $12k. And I'm also afraid that the halving news catalyst price pump has already happened this year instead of next year but that's just my speculation because I don't know what else would get us to moon and reach new highs.