The debate still rages over whether AI is in a bubble , but most agree that the top stocks sure do look expensive. While some see the bubble bursting outright , others are eyeing a situation where the momentum slowly seeps out. The red-hot AI trade has been the driving force behind the market's strong growth in 2025, but not all finance pros are optimistic that the gains can keep piling up at the same pace. David Miller, chief investment officer and senior portfolio manager of Catalyst Funds,