According to a well written post here, the new acceptable two letter words are not just baby talk. The four two letter words that will be allowed in tournament play effective December 1, 2014, DA GI PO TE, are going to change tournament play.
Just for your information, here is the existing list of acceptable two letter words, with thanks to The Phrontistery. (He has an extensive listing of Scrabble words for cloth and fabric that is fascinating.)
AA AB AD AE AG AH AI AL AM AN AR AS AT AW AX AY
BA BE BI BO BY
DE DO
ED EF EH EL EM EN ER ES ET EX
FA FE
GO
HA HE HI HM HO
ID IF IN IS IT
JO
KA KI
LA LI LO
MA ME MI MM MO MU MY
NA NE NO NU
OD OE OF OH OI OM ON OP OR OS OW OX OY
PA PE PI
QI
RE
SH SI SO
TA TI TO
UH UM UN UP US UT
WE WO
XI XU
YA YE YO
ZA
To give you the full flavor experience in a small shot, these are the new three-letter words that are are back hooks for those new two-letter words: DAS DEP DOH EMO EST FAH GIF GIS HOM HOO LAH LOR MAM MEH MES MMM MOI MUX NAV NUG OIK OMA OPA ORG OWT PAK POS REZ SHO SIG SOC SOH TEC TES TIX TIZ UMS UNI YAS YER YEZ.
(Remembering my 149 point play of "m-u-t-i-l-a-t-e" in 2009 in a Calgary tournament: post here.)