Frisco is a suburb of Dallas - solid development all the way up the Tollway from Dallas to the $5 billion dollar mile in Frisco. In fact, development is hot north of 380 in Prosper.
I wouldn’t call Denton a suburb, but it does have a commuter train to Carrollton where folks can switch to the light rail system into Dallas. (One more change of train will get you to Fort Worth). McKinney has been held back because Central expressway has been torn up between Dallas and McKinney at some point or another continuously since the 1980s and McKinney didn’t want to be on the rail system. It’s easier to get down the Rayburn toll road to DFW airport than it is to get to downtown Dallas. Perhaps McKinney should be called a suburb of Plano and Frisco.
Terrell probably isn’t a suburb of Dallas yet, although Rockwall certainly is.
Both Allen and McKinney declined to join DART, so the light-rail stopped in Plano.
Now, all of the people in Allen and McKinney drive to the park & ride station in Plano and take the train. The parking lot was expanded TWICE, and it still filled up by 7:00 AM.
The complaints got so bad that DART finally instituted a fee for parking. Anyone that lived in a city that pays DART taxes (1% sales tax rider) can get a parking sticker that exempts them from the fee.