I know that free sites are kept going as one of my relatives passed away about four years ago and his site is still there.
Of course, we can also have a second free site in Tribalpages with the most important information and photo's etc and this will ensure that something remains.
To create a GEDCOM file in FTM ...
Open a family file
Select Copy/Export Family File from the File menu.
Under Save as type, select GEDCOM. If you want to save only part of your FTM file as a GEDCOM file, first display an ancestor, descendant or hourglass tree showing the individuals you want to include.
Then pick Copy/Export Individuals in Tree from the File menu and select a file name and folder for the GEDCOM file. Make sure the file ends with a .GED
I am not envisaging anyone missing my paid site much after I am gone. I have purchased a DVD of the site and this will be passed on. However discs and flash drives also have a limited life.
If my descendants are interested they will do something. If not, I will not be around to be worried by this.
I'm doing this mostly for my Grandson, but there are cousins out there that might have an interest.
Buying the DVD and giving them out to family helps. Be sure to contact who ever you can, in your family, and let them know the tree exists.
Don't forget to create a GEDCOM as a backup that can be passed to anyone that wants to create their own site.
Robert suggested converting a Gedcom into a readable form. I have been looking at that and so far have not found exactly what I want. Ancestral Author looks the best so far but I have yet to fully get to grips with the instructions. Will look at that further when I get time.
Print your tree in book form is another way that has been discussed in this forum before. Some family history programs have the program to do this. eg Roots Magic.
Personally I will not rely on a long life for my tree in a Family History site. I may print it in book form if I live long enough to get around to doing that. With changes in systems that will occur over the next 100 years maybe a book is the best ?.