Concerns have been expressed about the impact of the policy on the most vulnerable.
Ministers are concerned about the rising cost of the pass, with 880,000 people expected to be eligible by 2021.
In the Senedd on Tuesday Mr Skates said: "Any person who holds a concessionary pass at the time the changes to the law are made will not lose their entitlement to that pass in any circumstances".
It is the first time the government has stated when the changes would come into effect. According to a recent consultation, pass-holders represent about 47% of bus journeys in Wales.
The changes will need to be introduced through new legislation.
The minister said the number of people paying to use buses needed to rise.
"That's why we're looking at a broad vision of improving the attractiveness of travelling by bus," he said.
"We're looking at fare systems that currently operate in different parts of the world, which I think are very interesting, in order to make bus travel more affordable to the individual".Meanwhile Mr Skates told AMs that the website handling a renewal of the bus pass scheme has been improved after it crashed in September following a large number of applications.
All bus pass holders need to renew their pass before 31 December. Mr Skates told AMs that there had been around 210,000 applications on the website.
Figures showed there were about 730,000 passes in circulation at the end of 2018.
Mr Skates said:
I applied for mine online Monday and it was relatively simple procedure , though of course I have no idea how long it will take to process."Due to the huge surge in demand on the first couple of days, the website was taken off line and during this time significantly more capacity was built and extensive capacity testing took place, in partnership with Age Cymru and the Older People's Commissioner for Wales.
"Paper applications were available to download from the Transport for Wales website, by post on request, via the help line and available for local authorities."
You can access it here.
Given that the address on the paper forms is
Concessionary Travel Card
PO Box 55
PO Box 55
I wonder how many people are actually working on the project and whether they can cope with the paper applications?.
As a volunteer in ny local Library we have been inundated with request for application forms by people who for a number reasons can not use the online service.
But whereas online you only have to supply your current card number age and current provider . The application form asks for more details and Evidence of eligibility* 60 and Over to and you’ll need to send your completed application form along with two forms of evidence of your address and one form of evidence of your age (see Application Form Guidance for details).
You need to fill in the number of your current card so why cant it be dealt with in the same way as the online application.
Given that it is possible that applications by post may outweigh those online it may be that someone has not thought the process through.
Will there be an extension beyond 31 December 2019 if those applications already received have not all be processed.
OUr AM's should seek reassurances from Mr Skate.