In APA 6th edition style, if a reference has more than seven authors, the correct style is to give the names of the first six authors (in the form Surname, Initials), followed by three dots, and then the name of the last author (Surname, Initials). It is not correct to use a horizontal ellipsis (“…” or … in XML); instead, three periods (.) with spaces between them should be used.

Here is an example of a reference with more than seven authors formatted in APA style: 

Istrail, S., Sutton, G. G., Florea, L., Halpern, A. L., Mobarry, C. M., Lippert, R., . . .Venter, J. C. (2004, February 17). Whole-genome shotgun assembly and comparison of human genome assemblies. Proceedings of the National Academy of Sciences of the United States of America, 101(7), 1916–1921.

See this page for more information about APA style. For differences between APA's 5th and 6th editions, see here and here.