You're talking about 2140 but I would be worried much sooner, unless you believe the market cap will double after each halving.
Two more halvings and the security of Bitcoin could be in great danger due to economical factors and before this happens we will see higher centralization due to less companies mining it.
Where is, in your opinion, the limit between "secure" and "not secure"?
As I wrote in my last post, the hashrate would probably go back to 2018/19 levels if the complete block reward was cut. It will be a bit higher due to Moore's Law. Is that not secure enough?
Just a small comparison:
Bitcoin today has a block subsidy of roughly 200000 USD (65000 * 3.125). Transaction fee income is about 10000-20000 USD per block. A block is generated approximately all 10 minutes.
Litecoin has a block subsidy of roughly 500 USD, 4 blocks per 10 minutes, so the miner income is about $2000 per 10 minutes.
So LTC has only 1% of the current Bitcoin subsidy, and in addition there are no relevant transaction fee rewards. But it is considered safe enough for many exchanges to accept deposits of less than 24 confirmations (24 confs are equivalent to 6 Bitcoin confirmations, i.e. "one hour of confirmations"). And it is also safe enough that financial companies are basing regulated products on it (e.g. the CoinShares/ETC Group ETPs).
Litecoin can also serve as a model to see what could happen if the long term price increase is not pronounced enough to balance the subsidy decrease due to halvings. Miners income is thus now less than some years ago.
So in general I'm a bit more optimistic. I think Bitcoin is now much more secure that it needs to be, and after several halvings more, it will be likely that it is still secure enough - probably even in 2140.