what do you intend to do with it?
one way to help preserve the quilt is to get netting in as close a color to the worn-out area as possible. take tiny pick-stitches all around the hole, so that the hole is neatly encased in the netting. when you're satisfied that it's as secure as it can be, then trim the netting close to the hole, being very careful not to go over where the hand stitches are. the netting will keep the batting and the surrounding cloth from shifting or further wear.
now! if you want to display it, stop right there and display it. think of the displays of the egyptian tombs. where the original stones are missing, they filled in with plaster. everyone knows they are there to hold it all together, not to fool you. same thing. the netting will just just be a necessary evil holding the original together. nothing to do about that without GREAT cost. i mean totally restoring all the worn spots with fabric from the era.
if you intend to use it, don't. the entire thing will fall apart in no time at all. even light and heat are bad for it at this point. keep it out of the sun. not hanging is very important - it's own weight will tear it. fold it neatly and display it on a sofa or bed, carefully removing it before the furniture is used. refold carefully and often. the fibres will actually break if left in a fold for too long. it's a real pity that someone didn't take care of it, but it was probably a utility quilt and well-used for many years.
good luck with it and enjoy it for many more.
p.s. never, ever cover it with plastic. moisture will get in and mildew will appear. let the fabric breathe.