1- After TMP 4E core rulebook, what other 4E material is available now and in the near future? The timeline website is not clear on this/does not have a news section. Only Chris has that answer. The only "canon" material is the game modules PF (Project File) 01 through 10. Each has more equipment, tables, maps, vehicles, and facilities than came with the the 3rd edition. You will just have to adapt where necessary to 4th if it is even necessary.
2- Are additional TMP 4E resources going to be made available in digital format? Pdfs in this forum. Chris Garland is the sole source for what is going to happen with 4th edition.
3- When will a GM screen and dice be made available for purchase?
There is a thread here with inputs to make your own. Search should turn that up. It is incomplete as each PD has preferences.
4- Which of the many TMP fan sites forums are more TMP 4E new GM friendly and conductive to good discussions and gaming resources?
Goodness..... This and Google + are the only ones with any activity that I know of. 3rd edition came out in the 1970s, whole forums have come and died.
5- Are there any good YouTube videos you can recommend that show the basics of the game/how to play? Using the Youtube search engine provided this.
Gameplay
Request: Can you make available more pre-gens PCs and blank character sheets on Drivetrurpg.com? As suggested the Blank character sheet is free to download from Timeline Ltd. Google suggested others.