Signals intended for the Lower 48 United States will only be permitted to use 4000-4200 MHz. Signals not intended for the Lower 48 can still use 3700-4000 MHz, assuming the regions and countries those signals are targeted toward don't go through with C-band reallocations of their own.
You will not be able to pick up signals in the 3700-4000 MHz range if or when cell phone companies in your local area start transmitting on those frequencies. To continue receiving C-band signals in the 4000-4200 MHz range, you will likely also need a new LNB that filters out interference from the new cell phone signals below 4000 MHz.
Are they going to use the 4000-4200 MHz frequencies on all satellites, or certain satellites? I hope they won't tie up this frequency on all satellites because the christian network we watch is on 4004mhz on Galaxy 16. Will the Titanium LNBF with the filters take care of the interference?