Bitcoin core will not even double the block size to 2 mb
SegWit already quadrupled the maximum block size to 4 MB. Your argument is invalid.
SegWit introduced a maximum block weight of 4.000.000 units (compared to 1.000.000 bytes).
A 'typical' (non-segwit) byte in a transaction has a weight of 4 units.A witness byte weighs 1 unit.
So, theoretically if all transactions would be segwit we'd have 4 times more transactions inside the blocks than pre-segwit.
But the block size itself (for the non-witness part of the transactions still is at 1 MB.