No. When you make changes to an existing product or membership level, this only affects new members signing up. 


For example, if you delete the expiration date from a membership level, it does not take away the expiration date for members that have already signed up for the level, additionally it will not reinstate members that are already expired. Any change you make will only affect new members who purchase that membership. 


To change elements for a current member's membership, you will need change their membership level to one that has the new desired attributes. So, it may be best if you keep the current membership level that you have, make it inactive and then create a new one, copy over access rights to that one and move everyone over. 


If you have a lot of members that you need to move over to the new membership level, you may find it easier to use the Import Wizard to update your members' accounts rather then doing each one manually.