Staying past expiration of B2 visa

[Thunderstorm]

My parents (Indian citizens) have a 10 year B2 visitor visa and have visited the US nearly every year. Every time they entered, their stay as per the I-94 was valid for 6 months stay, but always they left within 3 months. They are planning to arrive in the US in March 2021 from a trip to Canada, however their current visa will expire in May 2021 (after 2 months of entry). 

Q1. Will they still be given a stay (I-94) valid for 6 months, of will they be given an I-94 only valid up to the date of expiry of the B2 visa in May 2021? 

Q2. If they are given a I-94 for 6 month stay (past the expiry of the B2 visa), are they eligible to file for an extension of stay (I-539) during this time to stay an additional 6 months (even if the B2 visa is expired)?

The guideline says that one of the conditions is that "Your nonimmigrant visa status remains valid". In this case, does the nonimmigrant visa status refer to the visa itself, or the I-94? 

Thank you for your guidance. 

[pontevecchio]

The visa lets them enter. The I94 dictates the duration of stay. The visa is an entry document.

In view of their frequent visits, I would not try to extend their stay beyond whatever is given to them.

[newacct]

1. for 6 months

2. yes