It is possible that transaction fees on the Bitcoin network could become high in the future, which could make it more expensive for normal users to open and maintain channels on the Lightning Network. This could lead to a more centralized system, as only users who can afford the high fees would be able to participate.
However, there are several potential solutions that could mitigate this problem. One solution is to increase the block size, which would allow for more transactions to be included in each block and therefore lower fees. Another solution is to implement a fee market that would allow users to bid for priority in the block confirmation process.

Additionally, there are several other layer 2 solutions being developed, such as the Plasma and the Optimistic Rollup, which are designed to enable scalability, increase the number of transactions that can be processed per second, and reduce fees.

Overall, while there is a risk that high transaction fees could make it more difficult for normal users to participate in the Bitcoin network and its layer 2 solutions, there are also several potential solutions that could help to mitigate this problem.