This is important to remember. It's obviously fun to project all these guys out, but at least some of them will never make the majors or at least never make an impact. That said, I don't see Maitan being in that group. Guys that are that highly regarded at that age almost always end up becoming very, very good major leaguers. He's the one I'm fine with getting pumped about.
I wouldn't even be that confident. The list below isn't cherry picked. It's the top signing bonuses ever paid out to J2 signing players as of 2009 (anything post that timeline wouldn't be a fair consideration at this point). Not a lot of hits, plenty of misses.
Michael Ynoa, 16, RHP, 2008, Athletics, D.R., $4,250,000
Miguel Sano, 16, SS, 2009, Twins, D.R., $3,150,000
Gary Sanchez, 16, C, 2009, Yankees, D.R., $3,000,000
Rafael Rodriguez, 16, OF, 2008, Giants, D.R., $2,550,000
Yorman Rodriguez, 16, OF, 2008, Reds, VZA, $2,500,000
Wily Mo Peña, 17, OF, 1999, Yankees, D.R., $2,440,000
Joel Guzman, 16, SS, 2001, Dodgers, D.R., $2,255,000
Angel Villalona, 16, 3B, 2006, Giants, D.R., $2,100,00
Juan Duran, 16, OF, 2008, Reds, D.R., $2,000,000
Adys Portillo, 16, RHP, 2008, Padres, VZA, $2,000,000
Guillermo Pimental, 16, CF, 2009, Mariners, D.R., $2,000,000
Jose Vincio, 16, SS, 2009, Red Sox, D.R., $1,950,000
Miguel Cabrera, 16, IF, 1999, Marlins, VZA, $1,800,000
Jesus Montero, 16, C, 2006, Yankees, VZA, $1,650,000
Jackson Melian, 16, OF, 1996, Yankees, VZA, $1,600,000
Jurickson Profar, 16, SS, 2009, Rangers, Curaçao, $1,550,000
Ricardo Aramboles, 16, RHP, 1998, Yankees, D.R., $1,520,000
Luis Sardinas, 16, SS, 2009, Rangers, VZA, 1,500,000
Michael Almanzar, 16, SS, 2007, Red Sox, D.R., $1,500,000
Esmailyn Gonzalez, 16, SS, 2006, Nationals, D.R., $1,400,000
Fernando Martinez, 16, OF, 2005, Mets, D.R., $1,400,000
Willy Aybar, 16, IF, 2000, Dodgers, D.R., $1,400,000
Carlos Triunfel, 16, SS, 2006, Mariners, D.R., $1,300,000
Luis Domoromo, 16, OF, 2008, Padres, VZA, $1,250,000
Juan Urbina, 16, LHP, 2009, Mets, VZA, $1,250,000
Chesler Cuthbert, 16, 3B, 2009, Royals, Nicaragua, $1,200,000
Roberto De la Cruz, 16, 3B, 2008, Cardinals, D.R., $1,100,000
Julio Morban, 16, OF, 2008, Mariners, D.R., $1,100,000
Kelvin De Leon, 16, OF, 2007, Yankees, D.R., $1,100,000
Alvaro Aristy, 17, SS, 2008, Padres, D.R., $1,000,000
Jharmidy De Jesus, 17, SS, 2007, Mariners, D.R., $1,000,000