whittonvillage - just correcting a few of your facts, in the spirit of accuracy ....
"The Th 2016 admissions point is in the centre of Teddington"
No, it's in the ward of Fulwell and Hampton Hill.
"Udney Park Road is the the catchment area of Th"
TH doesn't have a catchment area as such. It has an admissions point, but admissions around that point are unlikely to be circular, not least because of the River Thames and Bushy Park, but also because of the proximity of other schools. The Udney Park Rd area is well served by the very popular Teddington School, and Twickenham has Waldegrave and SRR (which does cater from children from Whitton by the way).
TH has been primarily proposed to serve SW Twick, Fulwell, Hampton Hill, North Teddington. It may also attract children from surrounding areas, including central Teddington and Whitton in the short term, but assuming it is succesful then its offer area is likely to shrink over time. More info here. There are certainly Whitton families who have offers this year, as shown by comments online.
"Udney Park Road is already connected by a number of bus links"
Wherever the permanent site is, public transport will need to adapt. However, TfL will cope with that. See here.
"You can only speculate as to why this is being considered"
You can only speculate because no formal statement has been made by the school, the EFA or the LA. The information has come from an unauthorised source, and has been embellished by gossip, so it isn't necessarily 100% reliable and the result is a little messy I'm afraid.