It should be interesting to see how much of the tech going into the FFG-X eventually gets retrofitted into LCS.
Unless the FFG(X) programme is awarded to either of the designs based off the two LCS classes, then I do not really expect a significant amount of modification or retro-fitting to the existing LCS vessels. After all, if neither of the two LCS-based designs are selected, that would suggest that the combination of cost and capability was insufficient when compared to other options. It could also quite easily be that of the systems which are found to be really useful and/or desirable aboard ship are ones which cannot be easily fitted to the LCS designs.
After all, the larger of the two LCS classes is still nearly 1,000 tonnes less displacement than the likely smallest of the conventional mono-hulls competing, that is nearly 25% lower displacement. 1,000 tonnes 'extra' displacement, or 2,000+ tonnes if one of the other two was selected instead, is a great deal of displacement. There would plenty of displacement to carry and support extra crew, fit more weapons and/or sensors, etc. It would also be worth noting that could also potentially increase the power generation capacity as well as the ability of a vessel to remain in an area before needing to replenish supplies.