Seen as "stay-at-home" winners in the coronavirus lockdowns, shares in Apple Inc , Facebook Inc, Amazon.com and Alphabet have surged this year and now account for nearly a fifth of the S&P 500 stock market value.
Bumper results from the iPhone maker last week pushed it past Saudi Aramco to become the world's most valuable publicly listed company and heading towards a $2 trillion valuation.
In a global markets research note sent to clients, Goldman analysts said the current rally could last until Labor Day in early September, but would be threatened by updates on vaccines.
"Approval could ... prompt the kind of rotation that started and petered out in May and early June, supporting traditional cyclicals, steeper curves and banks, and challenging tech leadership," they argued.
(Reporting by Tanvi Mehta in Bengaluru; Editing by Patrick Graham, Bernard Orr)