hello and welcome,
as per the details provided,your dentist
is trying to save the teeth with deep dental carries by root canal treatment
usually the strength of root canal treated teeth is very low since the teeth is nonvital.
your dentist"s plan is acceptable.
the output of the bridge placed can be predicted once the bridge is inserted into your mouth.
eventually,the spaces arised from extracted teeth has to be occupied with bridge to prevent mesial or distal drift of adjacent teeth causing mal-alignment.
Also make sure that,you are utilising both sides of teeth for chewing food equally .this will help in easy adaptation of new bridge.