Yes it is normal for an adjacent tooth to move into the extraction space(space in the bone of the tooth removed) in case of a long gap between removal and replacement of the tooth.
But nevertheless, your molar can be replaced even now just with addition of a few steps. If the space is less for replacement, space can be created with temporary braces as well.
Next Steps
Visit a nearby prosthodontist for consultation as they are experts in replacements of missing teeth.
Health Tips
There is nothing to worry. With new advancements in dentistry, there are a lot of options and ways to make space and replace missing teeth even after a long gap.