There are two relevant clauses in most life insurance policies: the contestability clause, and the suicide clause. Both apply to the first two years of the policy’s existence, but they are otherwise importantly different.
The contestability clause allows the insurer to investigate and deny claims if it turns out that important information was withheld when the insured was applying for the policy. So if someone had already been diagnosed with a terminal illness or was planning to commit suicide when they applied, failing to disclose that information would invalidate the policy (since it is likely the company would not have issued the policy in the first place had the applicant been honest).
The suicide clause simply says that the policy will not pay out if the insured commits suicide within two years of the policy being issued. It also requires the company to return any premiums already paid by the insured. After two years, the policy pays out as normal regardless of the cause of death. This is important because many people fail to file a claim due to the mistaken impression that suicide always invalidates a life insurance policy.
So what does this mean for assisted suicide? If other states follow Oregon’s lead, then the suicide clause will become more or less irrelevant because the Death with Dignity Act requires insurance companies to pay out the deceased’s life insurance policy regardless of when it was taken out. The contestability clause would still be relevant, however, because an insurer retains the right to deny a claim if the policy was obtained fraudulently.
Life insurance companies have been surprisingly unconcerned about this part of the Death with Dignity Act and seem uninterested in lobbying against it. I suspect this is due to a mix of the cost-balancing reasons that @keobooks mentioned and actuarial tables predicting that very few cases the insurer could expect to win would fall under the suicide clause while not also falling under the contestability clause. Therefore, it is likely that any new measures legalizing assisted suicide will follow the same pattern of granting an exception to the suicide clause while leaving the contestability clause in place.