As we known, the 2.4G wireless module of RB4011 don’t support wireless wave2, only 5G module do.

And we know the 2.4G modules is mounted on a card.

So can we upgrade this card to support wave2? Could Mikrotik make an upgrade card ?

While it's possible to replace it with another miniPCIe card, MT currently doesn't offer card with 2.4GHz radio that would be supported by wifiwave2 driver. AFAIK. And there's slim chance for wifiwave2 driver to include proper support for 3rd party hardware (but not impossible). It would have to include one of chipsets, supported by wifiwave2 driver.

Now you have only written what we all already know.
What we need to know is what 3rd party WiFi card uses one of the Qualcomm chips that wifiwave2 supports.
And it would be nice when MikroTik re-sells such a card within their product gamma, even nicer when they offer it to RB4011 buyers at a discount.