Shinkansen Last Day Golden Week?

Very helpful forum; been scouring it ever since I got a great deal on airfare for my first Japan trip. Now trying to plan an itinerary for an upcoming 9 day vacation there. Part of it would involve going to Osaka from Tokyo in the morning on the last day of Golden Week (May 5th). Will it be that busy at such a time? Will I be able to reserve a seat? Is there likely to be space for luggage (back of the train car?) since I want to take a folding bike with me.

The opposite direction is more busy than the direction you are traveling. And the afternoon is probably more busy than the early morning. Nevertheless, it is probably going to be rather busy.

I don't feel confident to predict how many trains will be booked out in advance, but I have the feeling that not all the trains will be booked out and that you have a good chance of making seat reservations on some train if you do so a few days in advance. I am afraid that hikari trains are more likely to be booked out than nozomi trains.

There is also a heightened risk that the space behind the last row of seats is occupied.

Thank you.

I'm thinking or hoping it will be ok since it'll be the morning & likely most ppl will be coming back to Tokyo rather then heading to Osaka.

Just be aware that you might be asked to put the folding bicycle in the bike bag.
http://www.kancycling.com/Getting_Started/Using_Bikebags.html