Have there been made any calculations how high the transaction fees for bitcoin main network could get in the future?
I currently have my BTC stored on a MultiSig cold wallet, which can't be connected to a lightning node. Do you think it's a better idea to move them to a lightning wallet like on electrum for example before the transaction fees get too high? I want to avoid paying a big amount just for one transaction in the main network
Even if the commission becomes high in the future, you will more than compensate for these costs with the profit you receive. The growth in the value of bitcoin will still be much higher.
If a MultiSig cold wallet provides a greater level of security than simply storing bitcoin on electrum, then I believe future high transaction fees can be neglected. Security and reliability of storage are now incredibly more important.
There is a balance between greed and safety.