It doesn't imply their marital status at all. No more so than Messrs. Jones and Wilson implies that they are in a homosexual union.
I would use the term Drs. X and Y.
But, there are certainly situations where you will need to address a married couple of doctors.
My wife and I experience this all of the time. She hasn't taken my last name, and we're both physicians.
She is Dr. N, and I am Dr. M.
I frequently get letters addressed to:
"The Doctors M" (incorrect due to her preference).
Doctors (or Drs.) M (incorrect due to her preference, again.)
Dr. and Mrs. M, (technically correct, but she finds it offensive).
Dr. and Dr. M (again incorrect based upon her preference).
Drs. M and N (Works well, no offense taken by anyone).
Dr. M and Dr. N (Also works well, no offense taken by anyone).
My personal preference is for Drs. M and N. I think it flows better. And, keeping up with the sexist traditionalism: Male first, female second. It keeps with the Mr. and Mrs. convention, and many will assume it to be so.
The other side-effect of her not having taken my name: I get called Mr. N frequently on vacation when a hotel's phone system brings the name up. Drives me batty.