I agree with the above view.
It is purely a tactical alliance for dealing with GE especially in tackling GRCs, like what Scroo says. Akin to how DAP, PAS & PKR cooperate during M'sian GEs.
So to read SDA's version that RP is 'joining them' or to hear the idea of RP 'merging' with SDA is really unbelievable ! SDP, WP, NSP, SPP, RP should just be themselves as the efforts needed for a merger is counter-productive & unrealistic & wholly unnecessary except for a spirit of goodwill cooperation during GE.
Note that despite all that talk of 'Barisan Alternative' resulting in Pakatan Rakyat Coalition, the key figure is Anwar Ibrahim, the undisputed (?) Opposition Leader who can command the (grudging?) respect of both PAS & DAP.
There is no such personality or leader in Singapore of enjoying such overwhelming popular & consensual support. And even in Anwar's case, the unity is relative & situational.
Let the whole thing simmer down.
To all the whole spectrum of Opposition Parties:-
Be polite & civil to each other & preferably give each other space & keep each other at arms length & comments of each other to themselves.