I think you have already answered your question - if you "don't want to learn new slider processes" then perhaps you should not upgrade.
If you are shooting jpegs, consider that LR4 will provide some processing benefits, but the real processing benefits are in using it with raw files.
If you are going to be "in the business" for at least a few more years, then you should consider investing the time in learning LR4 (Process Version 2012 or PV2012) as the results are definitely superior to anything I could get from LR3 (PV2012). Also, for your legacy images processed in LR3 using PV2010, you can still manipulate them in the PV2010 environment within LR4 as if you are in LR3. The Basic panel remains the same as in LR3 Develop module until you convert those PV2010 images to PV2012. In fact you can leave them as PV2010 images and just use the newer PV2012 interface with your new images.
Two positives that may apply to wedding photography...
- Exposure does a better job of brightening mid-tones;
- highlights (i.e. wedding dresses) can be beautifully tamed with the Highlights and Whites adjustments;
- higher quality detail can be pulled out of the shadows (i.e. church interiors, dark suits) using the Shadows and Blacks adjustments.
Re: losing presets - I didn't when I upgraded - everything was intact.
PV2012 is a learning curve, but I am finding new life in not only my current images, but images I previously processed in PV2010.