I think they realised that the Mod would take them longer than ever.
I mean, they must have been in contact with the Redsun2020 dudes who took 5 YEARS to make their mod... and since TCP had 20 times the detail and work input than it, they would have predicted maybe... 8 years of hard work? To satisfy the extensive storyline that they came up with.
Remember, they have lives too, some in Uni, some at work, so the Mod would have been too hard to complete.
Part1 just shows you how skillfull those guys were.
2027 will be good, you can bet on that, but I don't know if it will supercede Cassandra... that was Godly.