LG has been riding on a high the past months, as their flagship LG G3 has received critical acclaim and the OEM seems to be doing good in terms of sales (as compared to the other Korean brand and their fierce rival, Samsung). But this means also that they might need to focus on several product lines and let go of those that may be too "redundant."
Reports indicate that the one getting the axe might be the previously popular "Pro" line, previously known as the Optimus G Pro. It used to be the positioned as the more premium and bigger versions of the "G" line, but now that the non-Pro devices are gradually increasing in size as well, there is very little difference between the two lines of smartphones now. The G Pro 2 is 5.9 inches, while the LG G3 is already at 5.5 inches. Rumors are putting the upcoming LG G4 at 5.9 inches, so if it is indeed true, then the Pro series would indeed be irrelevant.
2015 is supposed to be the year of the LG G Pro 3 but it looks like the Korean OEM might be skipping launching that at the MWC in February. What they are focusing on now is to finalize the LG G4 in order to get that out in the market by the middle of next year. This is something that most are looking forward to, especially as the current flagship was a darling, particularly in the QHD display aspect.
While we might be saying goodbye to the Pro line soon, their other series will probably remain, as they seek other markets. The L series is for those looking for more low-end and cheaper smartphones while the F series is the middle ground between low and mid tier devices.