High speed train from Cinque Terre to Venice in December?

15/12 is the first day of the 2020 schedule. It should be finished by now, but probably just haven't been added to the data base yet.

Welcome to the forums, kelssh -
Firstoff, the Cinque Terre isn't a single location; it's a group of 5 individual villages - Monterosso, Vernazza, Corniglia, Manarola and Riomaggiore - so to work your train schedules, you're going to want to input your departure from the village you'll be staying in.

Also understand there are no direct (no changes) high-speed trains to Venezia S Lucia from any of them: you'll be changing trains at least once, if not more, along the way, and almost certainly that will be from regionale or reasonably fast intercity trains to a higher-speed making fewer stops. This trip is also going to eat up 5-6 hours or more no matter how you do it.

So just messing around with some departures from, say, Monterosso on the Trenitalia site, there ARE train combos listed although it's possible not ALL of them are up yet.

The high speed trains listed before Dec. 14 though are 4.5 hours in
length.

OK, it's possible to get it down to 5 hours with 2-3 changes and a combo of train types but using Monterosso and a date of next week, I'm not seeing anything that takes as little as 4.5 hours, and it certainly wouldn't be a direct high-speed from the CT unless I'm missing something (LOL, been known to happen!!!). What departure town are you using?

The 12/14 Trenitalia schedule does show a few 4.5 hour trains. They are Freccia La Spezia to Pisa, regional to Florence and Freccia to Venezia SL. Unless you're staying in La Spezia, you'll need to add some additional travel time from your Cinque Terre town to La Spezia. I also noticed that only trains from Cinque Terre to Venezia by way of Milan are on the 12/22 schedule, so there's a good chance the faster trains you want will appear when the trains via Pisa/Florence are added to the schedule. I don't know when that will happen, but I suspect it will be soon.

Unless you're staying in La Spezia, you'll need to add some additional travel time from your Cinque Terre town to La Spezia.

Aha. Therein lies the issue. The train combo you mention, Frank, is probably the very one I was seeing only with that added travel time from Monterosso plus wait time between trains:

Monterosso 07:27 - La Spezia Centrale 07:42 Regionale
La Spezia Centrale 08:16 - Pisa Centrale 09:04 Frecciabianca
Pisa Centrale 09:12 - Firenze S. M. Novella 10:01 Regionale Veloce
Firenze S. M. Novella 10:30 - Firenze S. M. Novella 10:30 Frecciarossa

For obvious reasons There are no high speed trains serving tiny villages with less than 1,000 inhabitants. For sure not before the high speed line between Genoa and Milan will be finished, but that's another story depending on how stupid politicians will be in 2025.

What you need to know now is that Trenitalia has uploaded only the schedules of high speed trains running after December 14. Since there are no high speed trains serving the Cinque Terre and only a few call at La Spezia, the site can show only strange routes using only high speed trains.

Rest assured that the 2020 schedules will be uploaded by December 14, that they will be very similar to the current ones and that nobody buys non-high speed tickets months in advance.

In short, enter your real departure station on trenitalia.com/tcom-en (hope you are not staying in a former navy base known as LaSpezia) and a day of travel before December 14: Those are the real schedules, travel times and changes.
Monterosso is the only village of the five that has a direct train connection with Milano Centrale where you can get on a direct middle-speed train to Venice. There are no real high speed trains calling at the Serenissima and I doubt it will ever happen.

If started from Monterosso al Mare, there is a IC train to Pisa Centrale. It costs a bit more but there is no need to change train at La Spezia Centrale so one less hassle. The rest of the trip is the same as outlined by Kathy.

If started from Monterosso al Mare, there is a IC train to Pisa
Centrale

LOL, we've taken that train the other direction (Pisa to Monterosso).