Is it possible to calculate (theoretically) , how many common addresses could derive from the seeds?
If there are 2048^12 different seed combinations (in 12-word BIP39) and each has 2^256 keys then we have 6.3X10^116 different addresses.
We have altogether in Bitcoin 2^160=1,46x10^48 different addresses, which is a smaller number than the first one.
I would like to know is there a limit to how many bitcoin public keys be generated using one seed phrase. Is it unlimited?
It is unlimited
If it's not limited then this would mean that wallets with different seeds would cause a clash of their addresses. Am I right?
You really gave a good point however I think there must have an explanation. I will wait for others answer.
As pooya said it is limited to 2^256 (in practical terms only 255)
However this is a very big number.
Every seed can create billions of addresses in each derivation path. That means billions of addresses in change addresses, in legacy, segwit, native segwit, etc etc
A collision , which is what you are talking about is impossible in practical terms. Billions of addresses randomly generated is hard for our minds to understand.
From antonopoulos mastering bitcoin: