Will the value change in bitcoin affect the recommended channel sizes?

If a single transaction can use multiple paths (MPP?) then it doesn't really matter what individual channel sizes are. Big channel routing nodes may be less relevant in the future...but are useful today. A highly interconnected network would seem to be more useful than a lesser interconnected network limited by peoples thoughts on 'ideal channel sizes'.

I'd go with - open the number and size of channels which works for you. Don't rebalance them and play the long game. The value of bitcoin will be whatever it will be and that's unknowable.

Yes, on the long term without a doubt the minimum recommended channel sizes will decrease. But there will never be a situation where a channel is too big. However it's true that 2 relatively smaller channels may be more beneficial in the future compared to 1 larger one. It also depends on your node and your goals. If you just want a node to send and receive payments, go with 2 smaller channels for more redundancy (in case one of the nodes goes down). But if you're a node operator trying to become profitable, go for larger channels instead because they are preferred by routing algorithm for obvious reasons.

However, as mentioned above, large adoption of MPP may change the dynamics. Payments will flood the network with many small transactions, thus even small nodes will participate in moving funds regularly.

Hey Hodler, this is a very good question, indeed! I've also been thinking 'bout this for a while now. If the value of bitcoin doubles, you will be able to send twice as much Fiat money with the same channel. Since lightning is meant for everyday payments and smaller amounts there might be no need for channels of this size anymore if btc is increasing in value more and more. But on the other handside would it be better for the network to have more channels with smaller capacity or lesser channels with more capacity? I think that might be the actual question we should ask. Any other thoughts anyone?

How many nodes do you reckon support MPP? Which softwares (Umbrel, Raspiblitz) support it?
I have no idea if I have ever forwarded an MPP yet ;')

Umbrel / Raspiblitz are just frontends. You are looking at the LN node implementation (LND/c-lightning/eclair)

As far as I know all major ones support it and most recent versions enable also sending them by default