When a couple of Pokemon Go players complained about the fact that the speed of hatching eggs in the game had rised significantly, no one knew it was not an outage but actually a change in the game brought in by its developers and it seems that it is something that is going to stay. Although there has been no official announcement, keen Pokemon Go players have concluded that the change is permanent. 

A report on the website PokemonGoHub stated, "We've received a growing number of reports from players in the US and AUS region that the speed at which they are able to hatch Pokemon GO eggs has been substantially increased. After taking a quick look in our own testing, we are able to confirm that either the Pokemon GO Egg Hatch Speed has increased or the frequency of tracking has been increased." The report went on to state, "Several players have reported that the distance tracker now works even while bikingand some claim that the tracker updates more often than previously used 4 - 5 minutes. We agree with the reports as it was evident from our own morning bike ride that the tracker is quite more reliable.

It looks like Niantic did one and possibly both things:

• increased the top speed at which the game will register the traveled distance
• increased the frequency of detecting the traveled distance"

A user on the website Reddit said, "Did some testing after hearing about the increase to refresh rate of GPS location and the 'walking' speed of being able to hatch eggs. After going different speeds I found roughly around 20 MPH is where it'll finally stop. I easily hatched a 10K egg by driving around my neighborhood for about 10 minutes. Anyone else do any testing of their own? Edit: Just to be clear I wasn't the one driving while playing."