The way I see, NVidia only has a few advantages ordered from most important to least:
1. Reserved fab space.
2. Highly integrated software.
3. Hardware architecture that exists today.
4. Customer relationships.
but all of these aspects are weak in one way or another:
For #1, fab space is tight, and NVidia can strangle its consumer GPU market if it means selling more AI chips at a higher price. This advantage is gone if a competitor makes big bets years in advance, or another company that has a lot of fab space (intel?) is willing to change priorities.
2. Life is good when your proprietary software is the industry standard. Whether this actually matters will depend on the use case heavily.
3. A benefit now, but not for long. It's my estimation that the hardware design for TPUs is fundamentally much simpler than for GPUs. No need for raytracing, texture samplers, or rasterization. Mostly just needs lots of matrix multiplication and memory. Others moving into the space will be able to catch up quickly.
4. Useful to stay in the conversation, but in a field hungry for any advantage, the hardware vendor with the highest FLOPS (or equivalent) per dollar is going to win enough customers to saturate their manufacturing ability.
So overall, I give them a few years, and then the competition is going to be real quite fast.