The simple answer I think is no - but the question is not very clear given some missing/conflicting information.

If you achieved Gold status in 2017 ("last year") and have a card with validity to 2020, that must because you were caught up in the IT meltdown and given a year extension (so Gold for remainder of year + next year + an extra year).

Your concern then I assume is that because you will qualify for BAEC Gold again based on your flying that this will "overwrite" the year extension.

I think the answer here is that it shouldn't, but if it does a call to the BAEC Gold line should fix this.

What doesn't make sense though is that if the Gold card you have is valid until April 2020, that means your qualifying year must be based on March 8th, so if you expect to achieve gold this year that means that you will have Gold status for the remainder of this year (until March 8th 2019) plus the next year, i.e. until the end of April 2020 (so no difference in any case ....)