Tier2 General Visa and dependent eligible for ILR

[Hansraj Deshpande]

Hello,
I got Tier 2 General visa (sponsored) and entered in the UK on 1st June 2015. My wife and daughter got dependent visa in Jan 2016 and they entered UK on 23rd Jan 2016. (daughter DOB 10-10-2015)
We all extended our visa in June 2018 for 3 more years (will expire on June 2021). I will complete 5 years and eligible for the ILR on 1st June 2020 (can apply 28 days prior) but my wife and daughter will not be eligible for ILR till they complete 5 years (23 Jan 2021) .

If I (main applicant) get ILR on June 2020, will my dependents (wife and daughter) visa expire or they can continue and stay in UK till they become eligible for ILR on Jan 2021?
in case their visa expires ( because main applicant got ILR) , then what type of visa they need to apply for to still become eligible for ILR in Jan 2021.

Thanks in advance..!!

HRD.

[CR001]

Their visas remain valid.