In a practical sense for all intents and purposes, IMO.. I believe it is safe to say that there is some means available to rule any suspect in or out through DNA testing. I believe it a good thing to keep hope alive that at any time this little girls murder can yet be solved conclusively.
It may not be standard and it may not be pretty but even 6 markers in the system is workable for starters given the backup available from older dna test results. The more markers you have to work with, more suspects are excluded not more included. So in effect, you would not generate any more matches by having more markers in the profile. If you can't generate a match with 6 markers, you would not do any better with 13.
Any suspect can still be tested.. if a viable case can be made. IMO
No suspects can be tested if they refuse, even someone convicted of a sexual child murder. They can be asked. Only a person convicted of three sexual crimes can be ordered to give a sample. Look for my interview on Canada am the day after morins acquittal. Or my statement to the press on the final day of the inquiry.