You partially answered your own questions:
"Going to localdb only for non-available features in Access."
Beyond that possible factor, it's impossible to lay down rules for you for your application. Primarily that is because only you know the application you might want to upgrade from accdb back end to SQL Server back end. Only you know where the bottlenecks and pain points are in your application.
Some things that are often mentioned, though, include data security requirements and data size (i.e. the 2 GB limit on accdbs). Again, if those are pertinent to your application, you should consider them.