It depends on a few factors, like where you are and if you have access to a bike box or bag (you can usually rent these or borrow them from someone.) As well, are you travelling in Ireland or elsewhere before or after the race? If so, you need to think about what you'll be doing with a big bike box or bag in your rental car or train, bus, etc. Not all rental cars are big enough to accommodate bike boxes, particularly in Europe.

My recommendation is to bring your own bike yourself. Shipping it separately can be expensive. You've got loads of time, so you can search through this forum for advice on whether you should use a bike box or bike bag. One alternative if you are traveling once you're there is to leave the bike at the airport in baggage storage. This can be affordable at some airports.

Take your bike in a box would be my suggestion. If you're flying try to get a direct flight, or if you have to connect try to have a long layover. I've been there 50+ times and had lost luggage 3+ times (incl. a bike). If it gets delayed you're screwed as Dublin Airport's delayed/lost baggage is ridiculously bad. I can give you more details on the issues if you're interested. I fly with a soft shell case and never had any problems, although I do put fragile stickers all over it.

I was there in August and my bike was lost. There were scant options for renting a TT bike and I almost ended up borrowing one from a local. I'm guessing someone will figure out they can make money by renting bikes for the competition though.