T2 Visa extension question

[elm3388801]

Hi,
I hold a 5 years Tier 2 general working Visa, which was issued from27/11/15(I was into the UK on 21/12/2015); and the visa will be valid until 14/11/2020, so it will be 37 days to 5 years.
So in this situation.
firstly, Do I need to extend my visa to apply for ILR at the end of the year 2020?
Secondly, If I do need to extend my visa in that time, Do they have a new salary threshold in that time?
Because I don't understand the sentence "you’re still earning an ‘appropriate salary’" on the office web page.

https://www.gov.uk/tier-2-general/extend-your-visa

Please give me a help if anyone knows or has a similar experience.

Many Thanks,