Difficult to judge how this might pan out. It has never been dealt with before.
The SNP have written to the Met saying that there should be a police investigation into the part played by Conservative Central Office. The police investigations so far have been in the key marginal seats that were involved. Apparently the difference between a Tory overall majority of 12 seats and them not having it was 901 votes. If Conservative Central Office people are drawn into this they could be charged with conspiracy. Worst case scenario for the Tories is that there are a dozen or more Tory MPs charged, plus their agents (joint responsibility) and the Conservative Party Chairman plus others from head office. There would undoubtedly be calls for MPs to be suspended from their duties from aggrieved members of the public who would, not unreasonably, feel that that the democratic process has been undermined.
The police have applied for "an extension" because normally a 12 month rule applies for prosecutions after elections. Here's a list of affected constituencies but it may not be complete.
Amber Valley, Broxtowe, Bury North, Cannock Chase, Cheltenham, Chippenham, Dudley South, Erewash, Kingston, Lincoln, Morecambe and Lunesdale, North Cornwall, Northampton North, Nuneaton, Plymouth Sutton and Devonport, Pudsey, Sherwood, South Thanet, Sutton and Cheam, Thornbury and Yate, Torbay, Weaver Vale, Wells or Yeovil.