What Dragon Age has done was change the appearance and tone in all 3 games but they are all still connected to one another story wise as characters makes appearances in all 3 games, locations are revisited and plots are continued.
With ME4, it looks like it is not a reboot, but rather an escape from the events of the ME trilogy by taking place in a new galaxy. That is not a reboot just cause it takes place in a new location. ME2 took place in a new location (Terminus Systems) but would you consider ME2 a reboot?
Besides, it will be hard to take place in the Milky Way considering the 3 possible endings of ME3 and how Bioware does not want to declare a canon ending. So to play it safe, they leave to a new location where the events of Shepard has no effect. That isnt a reboot, restart or a remake. It still takes place in the same universe as the ME trilogy, just in a different galaxy.
I am excited! 
On the contrary, there was no connection between DAO and DAII whatsoever. Other than Hawke being from Lothering, Cullen showing up and Kirkwall, and a few cameos from Alistair, Sandal, etc., there was virtually no connection between the two games. It wasn't until BioWare created the Dragon Age Keep, emulating the Mass Effect save import scheme, to try and connect all the dots together into one cohesive game. In other words, it was pure fan service to try and give people the illusion that their choices mattered, when things such as OGB, Alistair being king, etc. actually had little consequence or impact on the game. Now, folks essentially want another DAII, which is a new game that really has no parallels to its predecessor. We saw how that worked out last time...
Going to a new galaxy would be a reboot. Everything changes. The Terminus system was merely a new sector of the Milky Way. We still had access to familiar locations. In a new galaxy, there would be no connection to the Milky Way whatsoever. It is entirely starting over. BioWare will incorporate a few familiar species, but essentially everything would be brand new: races, worlds, etc., with little regard or respect for what made Mass Effect previously. This is far more than just "an escape from the events of the ME trilogy."
No, it would not be... We have explored 1% of the Milky Way. There were not many active Mass Relays and much of the galaxy was still unexplored. In other words, the events of the Shepard trilogy only had an impact on known sectors of space, not the entire galaxy (there are billions of stars that were never touched). BioWare doesn't need to "play it safe." They have created one of the most iconic franchises in recent video game history. Better to use what you have than start from scratch and hope people stay on board. You may be excited, but the idea of the Shepard trilogy having little to no effect and BioWare just inserting random fan service (look, there's an Asari, there's a Krogan, there's a Turian, this is Mass Effect after all) to go to a new galaxy is odd, not supported in the lore or any of the games, and unnecessary.