The 'fourth interview' is really only necessary if you're not applying for a position right away. It may also be less of an interview and more of an informal talk about the position opening and how you would make a good contribution.
Also, depending on how badly your leadership wants you in a TL role determines how the first two interviews go. If your STL really wants you to be a TL, the first two will quite smoothly. If you're bad at interviews (like I am) they may use them to get you ready for the big guy/gal.
And because I know it will come up, I'll just say it now:
DIFFERENT STORES MAKE DIFFERENT EXPERIENCES